322 A Preliminary Monograph of the 



XV.— A Preliminary Monograph of the North American Species 

 of Trogophlceus. 



BY THOS. L. CASEY. 

 Bead December 17th, 1888. 



In describing the components of a large genus of minute, 

 closely-allied insects, the question often recurs, whether or not 

 the labor is being usefully expended, and whether the descrip- 

 tions alone will enable future investigators to recognize the 

 species. The thought doubtless comes to some of us, that per- 

 haps after all it would be just as well to let all but the better- 

 marked species go unrecorded; but as long as the fascinating 

 nature of the subject gives rise to enthusiasm in the study of 

 microscopic articulates, we must expect descriptive work, and 

 when monographic, this should be made as complete as possible 

 in order to avoid ambiguity. To attain the desired object, 

 however, the question of subsequent identification becomes one 

 of vital importance. 



In order that any particular species may be recognized with- 

 out reasonable doubt, one of three courses must inevitably be 

 taken : 



1. To so preserve the type specimen that it shall be indestruc- 

 tible. 



2. To reproduce the type on paper by means of a drawing, 

 which shall be practically faultless, and large enough to display 

 all the characteristic details of sculpture and vestiture. 



3. To draw up a description in language so full, explicit, and 

 detailed that there can be no doubt of its effectiveness, provided 

 the conditions under which the specimen is examined, are the 

 same in general principle as those under which the original was 

 produced. 



In regard to the first condition, there can be no disagree- 

 ment as to the difficulty of preserving specimens with exposed 

 mounting from those engines of destruction — insect pests, mould 

 and human manipulation, and even when mounted in an in- 



